This invention relates to a method for manufacturing an electrode, particularly an electrode plate composed of glass-like carbon, which is used for a source for generating a plasma of a plasma processing device.
A plasma processing device is typically used in the case where the surface of a subject material such as a semiconductor wafer or the like is processed in a processing chamber by a plasma process such as plasma CVD, plasma etching, or the like to form a device such as a highly integrated circuit or the like on the surface of the subject material. The plasma processing device generally produces plasma of process gas for etching, formation of a thin film, or the like by a plasma source in a highly vacuumed process chamber to provide the subject material with etching or to form a thin film on the surface of the subject material. The plasma generating source is provided with, for example, an electrode to which a high frequency voltage is applied and an earth electrode pairing with the above electrode and produces glow discharge between the pair of electrodes in process gas as a medium to produce plasma.
Conventionally, particles are removed from a process chamber to an extreme to prevent adhesion of the particles to a fine integrated circuit since multiple integrated circuits formed by a plasma process are formed on one wafer in a high density (highly integrated circuit). Other than electric conductivity, the characteristics required for the electrode used for the plasma source include high purity and resistance to plasma corrosion to restrain the generation of the above particles. At present, an electrode composed of glass-like carbon is thought to be useful for the electrode which satisfies these characteristics. Various trials for developing a material used as the glass-like carbon electrode capable of limiting the generation of extremely fine particles have been made and various glass-like carbon electrodes have been proposed.
For example, various electrodes, in which the properties such as a purity, porosity, pore diameter, crystal structure, and the like are improved, are proposed in the following official reports. Disclosed in Jpn. Pat. Appln. KOKOKU Publication No. 7-115853 is a carbon material used for a plasma apparatus comprising a glass-like carbon material characterized in that the glass-like carbon material prepared by carbonized baking has a porosity of from 0.02 to 0.2%, the crystal lattice of the glass-like carbon material is not detected by X-ray diffraction, and the content of impurities is 5 ppm or less. In Jpn. Pat. Appln. KOKOKU Publication No. 7-114198, disclosed is an electrode plate for plasma etching comprising a glass-like carbon of high purity, which has the structural characteristics in which a maximum pore diameter of 1 .mu.m or less, an average pore diameter of 0.7 .mu.m or less, and a porosity of 1% or less. Jpn. Pat. Appln. KOKOKU Publication No. 8-14033 discloses an electrode plate for plasma etching characterized in that the electrode plate is formed of a plate material with a thickness of 2 mm or more, which is composed of glass-like carbon of high purity, there is substantially no grain boundary on the surface and inside the structure, and maximum pore diameter is 1 .mu.m or less. Jpn. Pat. Appln. KOKAI Publication No. 5-320955 discloses an electrode plate for plasma etching comprising a glass-like carbon having the characteristics including purity characteristics in which the total ash content is 5 ppm or less, the content of metal impurities is 2 ppm or less, and the content of total sulfur is 30 ppm or less; crystal characteristics in which the spacing of crystal planes (002) is 0.375 nm or less and the size of the unit lattice is 1.3 nm or more; and the material characteristics in which the specific gravity is 1.50 or more and the flexural strength is 1,100 Kgf/cm.sup.2 or more.
Also, the technologies which specify raw materials for the glass-like carbon are proposed, for example, in the following official reports. An electrode plate for plasma etching comprising a glass-like carbon produced using a phenol resin and a polycarbodiimide resin as the raw materials is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 5-347276. Also, an electrode plate for plasma etching comprising a glass-like carbon material produced using a polycarbodiimide resin as the raw material is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 5-347278.
Other than the above technologies, the technologies in which the configuration or surface shape of an electrode is improved have been proposed. For example, Jpn. Pat. Appln. KOKAI Publication No. 6-128762 discloses an electrode plate for plasma etching comprising a glass-like carbon in which Rmax indicating the surface roughness of the portion consumed by plasma is 6 .mu.m or less. Also, disclosed in Jpn. Pat. Appln. KOKAI Publication No. 7-22385 is an electrode plate for RIE made from glass-like carbon having a plurality of gas through holes formed by processing, wherein the inner wall of the gas through holes is formed of a material with a baked surface.
As above-mentioned, various material progresses in glass-like carbon used for plasma processors have been made and are conventionally proposed. However, the integrated circuit inevitably has the wiring structure, in which the width of a wire is in a level of a quarter micron, with recent progress in integration of an integrated circuit. Even extremely fine particles, which exhibit no problem in conventional plasma processors, cause troubles in recent plasma processing device. The cause and place enabling such extremely fine particles to generate are not clear so that there is the problem that it is difficult to prevent the generation of the extremely fine particles only by the conventional material progress.